[Zope] Transience read conflicts

[Dennis Allison]

We are seeing occasional read conflicts in Transcience.

Traceback (innermost last):
   [...]]
  Module Products.PythonScripts.PythonScript, line 323, in _exec
  Module None, line 6, in setSessionVariable
   - <PythonScript at /setSessionVariable used for
/questionbanks/questionbank_edit/queries>
   - Line 6
AssertionError: Assignment to "currentQuestionBank" failed
database read conflict error (oid 0x1205, class
Products.Transience.TransientObject.TransientObject)

Zope 2.7.3
Pythn 2.3

Transcience apparently throws an exception rather than serialize.
Is that a bug?

Is this a bug?